Iron sulfate and phosphite products fail to suppress snow mold on amenity turfgrass in Wisconsin

Abstract

Snow molds are an important group of diseases of amenity turfgrass in temperate climates. Acceptable control is typically achieved through one or two fungicide applications prior to snow cover, though there is increasing interest in exploring alternative control products such as iron sulfate and/or potassium phosphite. Previous research has demonstrated that poor snow mold control is achieved when these alternative products are applied once prior to snow cover, so the objective of this study was to assess their efficacy when applied repeatedly throughout the fall. Iron sulfate heptahydrate, potassium phosphite, and the fungicide propiconazole were applied six times, every 2 weeks, throughout the fall of 2019 at three locations in Wisconsin that typically produce high, medium, and low snow mold pressure. No reduction in disease relative to the nontreated control was observed at any location in response to the iron sulfate and potassium phosphite treatments. Propiconazole did provide effective snow mold control at the low and moderate pressure locations but not at the high pressure location. Both iron sulfate and potassium phosphite have shown efficacy against select turfgrass diseases, but do not appear to provide control of snow mold in areas where snow cover persists during winter. INTRODUCTIONSnow molds such as Microdochium patch (caused by Microdochium nivale), gray snow mold (Typhula incarnata), and speckled snow mold (Typhula ishikariensis) are the primary low-temperature diseases of amenity turfgrass around the world (Hsiang et al., 1999;Mann & Newell, 2005). Microdochium patch, also known as pink snow mold, is defined by roughly circular patches of tan-or reddish-colored turf 2-8 inches (5-20 cm) in diameter. Symptoms are typically most severe under prolonged snow cover but can also occur in the absence of snow following periods of cool (32-48 ˚F) and wet weather. The presence of a pink-colored ring Abbreviation: HDD, heating degree day.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.